The present embodiments relate to an arrangement and a method for the active vibration dampening of an x-ray emitter.
With tomography devices, two or three-dimensional images of an examination area of a patient are created for diagnosis or treatment purposes. For example, three-dimensional slice images are generated with a computed tomography device. The structure of a computed tomography device includes a gantry (e.g., a supporting portal) having a stationary supporting frame, in which a rotary frame is mounted so as to be rotatable about an axis. A recording system is arranged on the rotary frame. The recording system includes an x-ray emitter and a detector arranged opposite to the x-ray emitter. Projections are acquired in a spiral manner from a plurality of different projection directions by rotating the rotary frame while simultaneously continuously advancing a patient resting on a couch apparatus in the direction of the system axis. Since 99% of the electrical energy used to generate x-ray radiation of the x-ray emitter is converted into thermal energy, the computed tomography device includes a cooling apparatus in order to prevent the electronic components from overheating.
During operation of the mechanical and electrical components of the tomography device, a noise level that is perceived to be unpleasant both by the patient and also by the operating personnel is produced. Interfering solid-borne sound waves and air-borne sound waves are produced, for example, by the rotation of the rotary frame, by the rotation of the anode within the x-ray emitter or by the operation of the cooling apparatus. A resonance element that amplifies the sound amplitude is formed by encasing the x-ray system. The patient is exposed to a particularly high noise level immediately in the tunnel opening of the gantry, through which the patient is moved during the scanning process.
One aspect with the configuration of a tomography device is therefore the minimization of the interference sound produced during operation of the tomography device. Two different approaches exist in order to prevent or minimize the propagation of interfering solid-born sound waves and air-borne sound waves in a tomography device. The interference sound generation may be directly reduced by optimizing the components causing the sound. For example, the solid-born sound wave propagation may be minimized during rotation of the rotary arm or rotation of the anode by using a noise-optimized rotary bearing. Optimization of this type is, however, associated with a very high cost outlay, and the achieved reduction in interference sound may not be adequate.
The sound propagation may also be prevented by using noise dampening matting. In order to reduce the air-borne sound propagation, the noise dampening matting is glued to the interior of the housing of the tomography device, for example. The solid-born sound propagation may also be minimized by using corresponding passive dampening materials at contact points provided to hold the components. An effective reduction in the sound propagation is, however, only achieved when the dampening material is a specific thickness. The construction volume that may be used for the dampening is, however, very restricted so that these measures may not be sufficient to reduce the interference sound to a desired level.
A tomography device with a counter-sound facility and a method for reducing an interference sound produced during operation of the tomography device is specified in the application DE 102008047814 A1. The facility includes a control unit for providing a counter-sound signal and a sound generation unit for converting the counter-sound signal into a counter-sound phase-shifted by 180 degrees with respect to the interference sound. The interference sound may be effectively reduced during operation of the tomography device.
The patent application US 2005/0281391 A1 discloses a computed tomograph, in which a vibration of a supporting frame is determined, and measures for cancelling out this vibration are taken on account of the vibration.